The present invention relates in general to recording and reproducing video signals. In particular, the present invention provides a method and apparatus for optimizing the recording and reproduction process by automatically adjusting various parameters of the recording process to compensate for variations in the quality of the recording medium, degradation of the record/playback head and the efficiency of the head/medium interface.
Technical advancements in the past several years in the field of video recording have brought the concept of providing a practical and commercially viable still video system (SVS) to reality. SVS camera and player/recording units have recently been demonstrated that permit the user to record up to fifty half-frame or twenty-five full frame still video images on a single magnetic recording disk. A standard still video format (SVF) has been developed wherein the twenty-five full frame still images are recorded on fifty recording tracks of an SVF recording disk.
Problems have been experienced in still video systems, however, with luminance (luma) and chrominance (chroma) signal degradation due to track to track variations of the recording medium. For example, many recording disks are known to have higher noise levels at track fifty as compared to track one. As a result, the luma signal/noise ratio (SNR) will decrease thereby producing a picture of degraded quality upon reproduction. The magnetic material on the disk may also be distributed in a nonuniform manner, causing variations in playback signal levels from track to track.
One possible way to eliminate the problem of reduced luma SNR described above would be to boost the recording current at the inner tracks of the disk. In such a case, however, it is necessary to determine the exact amount of current increase in order to avoid creating other problems. For example, the disk could be divided into two zones, one zone containing tracks 1-25 and the second zone containing tracks 26-50, to which two different recording levels would be applied. The higher recording current at track 26, however, may create an increase in intermodulation that was not present at track 25. Thus, it is necessary to ascertain the quality of each individual track of the recording disk and to adjust recording parameters accordingly in order to compensate for track to track variations, rather than relying on predetermined changes of recording parameters based on arbitrary groupings of recording tracks.
Other factors may also effect the reproduction of the video image in addition to the variations in disk quality, such as degradation of performance of the recording/playback head and the efficiency of the head/medium interface. It would therefore be desirable to automatically compensate for these additional factors while correcting for variations in disk quality.